Incomplete recovery of tree community composition and rare species after 120 years of tropical forest succession in Panama

Abstract

Determining how fully tropical forests regenerating on abandoned land recover characteristics of old‐growth forests is increasingly important for understanding their role in conserving rare species and maintaining ecosystem services. Despite this, our understanding of forest structure and community composition recovery throughout succession is incomplete, as many tropical chronosequences do not extend beyond the first 50 years of succession. Here, we examined trajectories of forest recovery across eight 1‐hectare plots in middle and later stages of forest succession (40–120 years) and five 1‐hectare old‐growth plots, in the Barro Colorado Nature Monument (BCNM), Panama. We first verified that forest age had a greater effect than edaphic or topographic variation on forest structure, diversity and composition and then corroborated results from smaller plots censused 20 years previously. Tree species diversity (but not species richness) and forest structure had fully recovered to old‐growth levels by 40 and 90 years, respectively. However, rare species were missing, and old‐growth specialists were in low abundance, in the mid‐ and late secondary forest plots, leading to incomplete recovery of species composition even by 120 years into succession. We also found evidence that dominance early in succession by a long‐lived pioneer led to altered forest structure and delayed recovery of species diversity and composition well past a century after land abandonment. Our results illustrate the critical importance of old‐growth and old secondary forests for biodiversity conservation, given that recovery of community composition may take several centuries, particularly when a long‐lived pioneer dominates in early succession.Abstract in Spanish is available with online material.

Reassembly of a tropical rainforest ecosystem: A new chronosequence in the Ecuadorian Chocó tested with the recovery of tree attributes

“…On the other hand, maximum tree DBH and basal area recover after 120 and 104 yrs, respectively. Basal area recovers at a similar time compared to a tropical forest in Panamá whose recovery was estimated after 90 yrs (Elsy et al, 2023). This shows that despite regenerating forests having a similar number of stems compared to oldgrowth forests in a relatively short period of time, the full recovery of their structure still takes 4x that time.…”

“…Even though there was no bias in elevation and land-use, analyses along chronosequences benefit from the consideration of biotic and abiotic environmental variation as potential explanatory variables besides the time of regeneration, including variables that are independent of recovery. The lack of such variables has led to criticism of chronosequence approaches (Johnson & Miyanishi, 2008;Elsy et al, 2023; but see Walker et al, 2010). Our abiotic baseline data across our chronosequence included temperature, humidity, soil composition, canopy cover, precipitation, and landscape composition derived from satellite data (Table S1).…”